Professional grade headphone amps

I've been wondering for quite some time now...are any of those professional wide profile (meant for use in studio racks) headphone amps with multiple outputs any good? I see loads of them on pro audio gear web shops...stuff like Behringer, Presonus, Samson, SM Audio, Rolls, Art Headamp, etc. They all range somewhere around 200-250 dollars for 4 to 6 outputs, and they in general have pretty good specs, certainly good enough (above what is audible) THD, SNR, frequency response, usually around 350 mW of power output per channel, etc., almost all of them have balanced XLR intputs as well, and on top of that they have some basic EQ settings as well. So on paper they're not bad, but how do they sound in reality?

Does anyone here have any experience with such types of amps and which headphones did you use?

I mean, how bad can they be, even for under 100 dollars? 'm seriously close to pulling a trigger on one of these...just for the sake of it, take it apart, see whats inside, maybe mod it with better components, etc.

They aren't "bad" in terms of the price but note they would have a lot of limitations. Just because they're "professional grade" doesn't mean they are the absolute best for that price, especially with certain headphones, for example those that have low impedance and require a lot of current (much more so if they're relatively inefficient), which is why in "audiophile" amplifiers which, just like with the use of the term "professional," should not be stereotyped always as overpriced (overhyped in some cases perhaps is a more fitting description) or simply overbuilt when you look at their power supply and power capacitors. For example, especially with those $100 rack mounts as opposed to what some use in studios like the SPL Auditor or similar, they are more likely used professionally with something along the lines of the K66 or the HD25 (like in sports events), but the manufacturer may not at all have tested them with the K701 for example, much less the HE500. Then there are electrostats that have their own high-voltage amps, or speaker amp transformers.

If anything the only real argument against getting these kinds of amps is that they're a lot larger and for that money you're paying for too many amplification channels, which is fine if you need them on a professional application. Still, if space isn't a problem, for $100 I'd rather trust these over many other cheap amps that aren't too transparent (and aren't any better driving some headphones). As for modding, it's hard to tell what can be done to these without someone who knows how to do such taking a closer look at the circuits, but chances are some of them might be using a headphone driver chip like that old Philips chip on older Marantz CDPs (or the newer TI chip), so replacing them isn't a likely prospect as the circuit is likely not able to work with different chips. Remember these are pro products, not "audiophile" products, which aside from the headphone choice and power supply design capability, means also that pros for certain headphones already find them good and transparent enough with instruments they know, while a lot of "audiophiles" don't even play any real instruments and go looking for certain sound signatures which at times is not as the recording engineer intended if not unnatural sound outright,* hence some "audiophile" amps and DACs/sources tend to either be colored (well, some progear are also "colored" or rather come in different flavors, like guitar amps) or give various users the capability to color it as they wish with swappable op-amps. As for the other parts, barring a total power supply overhaul to allow each of the discrete amps for example to provide current to eight K701s, I'd assume all other parts are good enough too.

*Not to say there is only one kind of accurate sound, because in some cases some for example prefer emphasis on the drums, others on vocals, others on the guitars, etc, but generally a good system will produce natural-sounding notes on all instruments regardless of such emphasis. Grados for example are fantastic for pecussion, although spatial information on the drum locations could be improved on the Prestige series. Still I have run into people who rave about some products and then when I try that one (or a pairing, or a whole system), I find for example a highly rated expensive headphone producing treble that reminded me of a cheap JBL GTO mylar dome tweeter, and got me to thinking if some people who had that headphone were just going by all the rave reviews and haven't actually heard enough quality guitars with great metal strings, because it sounded like plastic strings on that (a borderline ear-piercing SR325 sounded a lot more accurate than that one).

Thanks for the reply. I've been wondering about these amps for a long time. What actually got me interested was the video about the Burmester sound system in the new Mercedes S class that I've been watching. There you can see that mr. Burmester (who know's a thing or two about audio :P) has his HD800's plugged into a 4 channel headphone amp, Grapevine Headamp 4 if I'm correct. You can see it at 1:20 mark of the video: https://www.youtube.com/watch?v=6HnkRfPjN3Q .

Clearly an HD800 cable, and on several occasions HD800's are visible trough the video. So if he uses them (again, an engineer who makes high end sound systems and played music for his entire life), then it can't be bad. This is not a very expensive amp, about 250 dollars when it was new, and very old (from like 2001). Specs on it are also not that great, even compared to some cheap Behringer stuff, yet, it can't be that bad if it runs the HD800's good enough for a very demanding listener.

If he works in a very quiet studio where even the A/C isn't audible, then he can use those amps at such a low volume level he probably isn't anywhere near 0.05% THD, and won't need as much current out of them either. Also, again, the problem with a lot of similarly priced consumer/"audiophile" products is that they aren't actually "hi-fi" - between two amps under $200, the power supply would be comparable, and so the pro amp that has less coloration compared to a consumer product that adds unnecessary warmth is always preferable unless size is a problem. When you factor in for example a transparent consumer amp at $400 with a really clean and powerful output however that's when you can notice there's a difference in some headphones. I've tried the K701 off a Samson four-way headphone distributor before at a pro audio store here and felt like they didn't have any "oomph." There's neutral, then there's thin and makes me sleepy - not to compare apples to oranges but the Samson studio monitors there actually sounded like real music (I eventually ended up with a Grado a year later). Years and years later I tried it with a Burson Soloist and I would've bought both if I had enough money (also tried the K701 with my own Meier Cantate.2 and it was still a lot better than the console). Still, if the choice was between oversized pro amps and cheap consumer amps, as long as size isn't the problem then definitely go with the pro amps. With more expensive amps, well, the pro amps with huge power supplies and running in Class A tend to be waaaaay more expensive than consumer amps, like Sugden and SPL, so I'm not one to buy them new (heck, who am I kidding - I haven't bought any audio gear new since my speaker days).

A little OT - their installation on the S-Class is only great for people who don't really want to fuss around with their car's audio system, and want to share the sound with the front and rear passengers. If you don't give a rat's arse about what the passengers would hear, especially if the occasional passengers you have in the car at the very least have no idea what imaging is anyway (if not tone-deaf), a fully active system applying time alignment processing with custom delays on each tweeter, midrange, and midwoofer relative to the subwoofers and each other will still do better recreating a proper image on the dashboard (provided you know what you're doing). That one also uses similar processing but they went as far as putting a tweeter (likely a fullrange driver) in the front, simulating a surround system, to help center the image, the same way that in some rooms a center channel speaker is better than a 2.0 or a 4.0 with a phantom center.

If he works in a very quiet studio where even the A/C isn't audible, then he can use those amps at such a low volume level he probably isn't anywhere near 0.05% THD, and won't need as much current out of them either. Also, again, the problem with a lot of similarly priced consumer/"audiophile" products is that they aren't actually "hi-fi" - between two amps under $200, the power supply would be comparable, and so the pro amp that has less coloration compared to a consumer product that adds unnecessary warmth is always preferable unless size is a problem. When you factor in for example a transparent consumer amp at $400 with a really clean and powerful output however that's when you can notice there's a difference in some headphones. I've tried the K701 off a Samson four-way headphone distributor before at a pro audio store here and felt like they didn't have any "oomph." There's neutral, then there's thin and makes me sleepy - not to compare apples to oranges but the Samson studio monitors there actually sounded like real music (I eventually ended up with a Grado a year later). Years and years later I tried it with a Burson Soloist and I would've bought both if I had enough money (also tried the K701 with my own Meier Cantate.2 and it was still a lot better than the console). Still, if the choice was between oversized pro amps and cheap consumer amps, as long as size isn't the problem then definitely go with the pro amps. With more expensive amps, well, the pro amps with huge power supplies and running in Class A tend to be waaaaay more expensive than consumer amps, like Sugden and SPL, so I'm not one to buy them new (heck, who am I kidding - I haven't bought any audio gear new since my speaker days).

A little OT - their installation on the S-Class is only great for people who don't really want to fuss around with their car's audio system, and want to share the sound with the front and rear passengers. If you don't give a rat's arse about what the passengers would hear, especially if the occasional passengers you have in the car at the very least have no idea what imaging is anyway (if not tone-deaf), a fully active system applying time alignment processing with custom delays on each tweeter, midrange, and midwoofer relative to the subwoofers and each other will still do better recreating a proper image on the dashboard (provided you know what you're doing). That one also uses similar processing but they went as far as putting a tweeter (likely a fullrange driver) in the front, simulating a surround system, to help center the image, the same way that in some rooms a center channel speaker is better than a 2.0 or a 4.0 with a phantom center.

Funny, I just found out that Grapevine Headamp 4 is actually made by SPL, didn't realize it at first. But yea, that's what I'm worried about with these amp, that they might be too thin or analytical. I mean, they're designed for studio monitoring, not listening to music, so they might be tuned to give a more clear insight into the mix, rather than musicality or some pleasant coloration. But then again, I've never really noticed much difference between headamps. I mean, so far I've owned the Project Headbox SEII (150€), Little Dot MkIII and MkV (both around 200€), Nuforce HDP (500€), NAD D1050 (500€), Musical Fidelity V-CAN II (100€) and Musical Fidelity M1HPAP (700€), and on top of that I've tried multiple integrated amplifieirs and receivers headphone outputs (probably like 30 of them, I went crazy last summer and took my headphones into every hifi shop in my city) and soundcards, best of which for headphones were the Asus Essence ST (200€) and Onkyo A5VL (400€). As you can see, prices vary from cheap to quite expensive, but to be honest, they all tend to sound like 95% the same, the only real noticeable difference being the Little Dot MKIII since it's a tube amp. All the SS amps sound 95% the same to me, even with Beyerdynamic T1's or K701's which are my most revealing headphones, and even using low impedance headphones out of 120 ohm output impedance integrated amplifier only minimally changes the sound signature. The only really noticeable differences between amps that increase the listening pleasure are the noise levels and channel balance, which is worse in cheap amps, almost always in my experience. Other than that, I'd be hard pressed to differentiate the V-CANII from the M1HPAP in a blind test at a normal listening level, even though one costs 7 times more. Ok, maybe it has a bit more weight in the bottom end and a bit bigger sense of space, but that comes from coloration, not neutrality or transparency, definitely not worth 7 times the price. Hell, plugging the T1's into an iPhone and comparing the sound to the M1HPAP is quite interesting. I know a lot of people would find it ridiculous, but at the same volume level, playing the same track trough the M1 fed by the iPhone, or plugging the headphones directly into the iPhone, sounds pretty much identical. Differences might be there, but they're so slight they're virtually not noticeable and definitely don't change the listening experience.

That's why I'm kind of thinking that getting a Class A pro amp with several outputs, each capable of driving several headphones in a decent manner acting pretty much like a wire with gain, would be quite nice and decent value for money. I'll see if I can arrange a listening session with some of these amps in one of the stores, I would assume they'd be willing to do that.

Funny, I just found out that Grapevine Headamp 4 is actually made by SPL, didn't realize it at first. But yea, that's what I'm worried about with these amp, that they might be too thin or analytical. I mean, they're designed for studio monitoring, not listening to music, so they might be tuned to give a more clear insight into the mix, rather than musicality or some pleasant coloration.

Actually the analytical professional amp to me isn't necessarily the opposite of what I understand to be "musical." Musical to me is great PRAT I can tap my feet to, and at times what other people deem "analytical" has a lot better PRAT - with better controlled and detailed bass, fast decay, etc - than what some people consider as "musical" - which is warm but sometimes obviously coloring the lower midrange down to the bass, with wobbly bass decay. Feist's "One Evening" has a bass beat that immediately betrays certain amps - even the very clean-sounding Digital Designs amp in my car driving Focal Polyglass mids was obviously less nimble than the NAD304 I had for example (yes, I took an extension cord and hooked it up to the car processor and speaker cables).

Of course, there are amps that on initial listen are neutral or analytical, but then the more I listened I paid more attention to the microdetails and found the PRAT to be less musical (by my definition). Oh, and just hearing that SPL made the Grapevine got me interested in it too - I think I'll get one for when a friend sets up his home studio (yeah, my amp, but I'll give it to him so he can't outright refuse us going over to his house's roofdeck to use his new home studio and his gas grill!).

Quote:

Originally Posted by derbigpr

But then again, I've never really noticed much difference between headamps. I mean, so far I've owned the Project Headbox SEII (150€), Little Dot MkIII and MkV (both around 200€), Nuforce HDP (500€), NAD D1050 (500€), Musical Fidelity V-CAN II (100€) and Musical Fidelity M1HPAP (700€), and on top of that I've tried multiple integrated amplifieirs and receivers headphone outputs (probably like 30 of them, I went crazy last summer and took my headphones into every hifi shop in my city) and soundcards, best of which for headphones were the Asus Essence ST (200€) and Onkyo A5VL (400€). As you can see, prices vary from cheap to quite expensive, but to be honest, they all tend to sound like 95% the same, the only real noticeable difference being the Little Dot MKIII since it's a tube amp. All the SS amps sound 95% the same to me, even with Beyerdynamic T1's or K701's which are my most revealing headphones, and even using low impedance headphones out of 120 ohm output impedance integrated amplifier only minimally changes the sound signature. The only really noticeable differences between amps that increase the listening pleasure are the noise levels and channel balance, which is worse in cheap amps, almost always in my experience. Other than that, I'd be hard pressed to differentiate the V-CANII from the M1HPAP in a blind test at a normal listening level, even though one costs 7 times more. Ok, maybe it has a bit more weight in the bottom end and a bit bigger sense of space, but that comes from coloration, not neutrality or transparency, definitely not worth 7 times the price. Hell, plugging the T1's into an iPhone and comparing the sound to the M1HPAP is quite interesting. I know a lot of people would find it ridiculous, but at the same volume level, playing the same track trough the M1 fed by the iPhone, or plugging the headphones directly into the iPhone, sounds pretty much identical. Differences might be there, but they're so slight they're virtually not noticeable and definitely don't change the listening experience.

Yep, there are a lot of decent Class A/B and Class A amps out there, and even across both general power supply topologies you can have any two amps sounding generally the same. As I posted above however, sometimes it's in the PRAT and microdetails that one can pick out one amp over another; and as in my previous post, sometimes it's how well one amp does with one headphone over another (Burson on AKG x70x). The key really is how much more one should pay for these (not really so) subtle improvements, and as it stands I still consider my Cantate.2 (got it used though) well within the nice sweet spot.